Contamination-resistant fuel pump with eccentrically located drive shaft



Dec. 31, 1968 s. E. P TOS 3,418,942 CONTAMINATIO ESIS T FUEL PUMP WITH ECCENTRICA LOCATED DRIVE SHAFT Filed Oct. 13, 1966 INVENTOR. (STEPHEN E. PA RTOS ATT United States Patent 3,418,942 CONTAMINATION-RESISTANT FUEL PUMP WITH ECCENTRICALLY LOCATED DRIVE SHAFT Stephen E. Partos, Mamaroneck, N.Y., assignor to Avco Corporation, Stratford, Conn., a corporation of Delaware Filed Oct. 13, 1966, Ser. No. 586,441 6 Claims. (Cl. 103-173) ABSTRACT OF THE DISCLOSURE A reciprocating piston pump, housed within a cylindrical casing, is provided with a wobble plate for actuating the pistons. The wobble plate is driven by a drive shaft which is eccentrically positioned with respect to the axis of the casing. A portion of the output from the pump is filtered and used for supplying contaminant-free fluid to the bearings.

This invention relates to a reciprocating piston pump having a novel means of Wobble plate actuation allowing eccentric location of the drive shaft and having novel features for increasing the resistance of the pump to contaminants in the pumped fluid, and increasing the loadcarrying capability of the bearings.

The conventional prior art wobble plate type piston pump utilizes a plurality of pistons located symmetrically about the axis of the drive shaft. In known prior art pumps of this type, actuation of the pistons is accomplished either by the rotation of the wobble plate on the axis of the driving shaft, the wobble plate being positioned at an angle with respect to the shaft, or by rotation of the piston block.

In certain applications it is necessary that the drive shaft be located eccentrically with respect to the pistons. This invention provides a non-rotating wobble plate with a stationary piston block for permitting such an arrangement. In addition, this invention provides bearings with greaty increased load-carrying capabilities, and also means which enable the bearings to function durably when submerged in fluids containing solid abrasive contaminants.

Furthermore, this invention provides a novel piston design that combines in an integrated unit the useful features of dynamic piston seals and of piston wear sleeves which enable the cylinders and pistons of the pump to resist the abrasive action of the solid contaminants carried in the fluids pumped.

It is an object of the present invention to provide a wobble plate driven piston pump in which an eccentrically located drive shaft imparts a nutating motion to a nonrotating wo'bble plate.

Another object of this invention is to provide means for maintaining the bearings and seals of such a wobb-.e plate pump resistant to contaminants in the pumped fluid.

For further objects and advantages of this invention reference should now be made to the following detailed specification in which:

FIGURE 1 is a cross section of a preferred embodiment of this invention; and

FIGURE 2 is a section taken through the line 22 in FIGURE 1.

Referring to the drawings, the pump includes a cylindrical housing, generally indicated at 10, having similar upper and lower portions 12 and 14. Both portions 12 and 14 are provided with a plurality of bores forming opposed piston cylinders 16. Pistons 18, adapted to slide axially within the cylinders 16, are provided with unique combined piston seals and wear sleeves 20. Each combined piston seal and wear sleeve is made of an elastic plastic maice terial, such as polyurethane, which may extend the entire length of the piston, the end of the combined seal and sleeve adjacent the piston head being urged against the walls of the cylinder 16 by means of fluid pressure. The piston 18 works against fluid in the cylinder 16 in opposition to return springs 26 constrained within the cylinder walls by a disk 24 mounted on a pin 25.

The pistons 18 are driven on the discharge stroke by a Wobble plate 28 which is in turn nutated by a shaft, generally indicated at 30, keyed at 32 to a motor or other source (not shown). The shaft is a composite structure made up of several elements serving to non-rotatively wobble or nutate the plate 28. The elements include a cylindrical shaft portion 33 made integral with a wedgeshaped disk 34. Integral with the disk is a cylindrical shaft portion 36 extending from the wedge-shaped disk at an angle with respect to the axis of the cylindrical portion 33. A second wedge-shaped disk 38, complementary to the disk 34, is attached with its integral cylindrical shaft portion 40 to the cylindrical portion 36. As the various pump units are assembled, the wobble plate 28 is positioned on the shaft portion 36 between the disks 34 and 38 on thrust bearings 42 and 44 and a radial bearing 46. The shaft rotates within bores provided in the upper and lower housing portions 12 and 14 in radial bearings 48 and 49 and thrust bearings 50 and 51. The shaft 30 is provided with an axially extended channel 52 and a plurality of cross channels 54 for providing the passage of the fluid pumped under pressure to the surfaces between the shaft 30 and the various bearings.

The bearings 42, 44, 46, 48, 49, 50, and 51 are made of carbon graphite and are relatively loosely fitted between the stationary and rotating elements. This loose mounting permits the rotation of the various bearings to reduce the relative speeds between the bearing races and the rotating elements, and hence tends to increase load-carrying capability and reduce bearing wear.

The housing portions .12 and 14 are also provided with a plurality of bores providing passageways for the fluid being pumped. Without going into detail concerning the specific construction of the various passages, it is noted that the pump has inlets 56 and 58 and outlets 60 and 62. The inlets 56 and 58 communicate with a passage 64 which in turn communicates with bores 66 in the upper and lower halves 12 and 14. There is one such bore 66 for each cylinder 16, and each contains a spring-biased inlet valve 68 which automatically closes on the discharge stroke of the respective piston 18, and opens on the suction stroke. On the discharge stroke the fluid being pumped passes through a passageway 70 to valves 72 in the upper and lower halves. On the discharge stroke the valves 72 open, while on the suction stroke the valves close. Fluid is pumped through each of the valves 72 to the outlets 60 and 62 into a bore 74. A portion of the pumped fluid is fed via a bore 76 and through a wash flow filter 78 back to the axial passageway 52 in the shaft 30. This filtered fluid, under a pressure in excess of the inlet pressure, passes through the cross channels 54 and is forced into the spaces between the shaft 30 and the various bearings. Since the fedback filtered fluid is under pressure, the inlet fluid is prevented from entering these spaces, and hence only filtered fluid is permitted to enter between the bearings and the bearing races. This tends to render the pump bearings resistant to any eroding contaminants in the pumped fluids.

Another feature tending to provide long wear is the fact that the wobble plate is eccentrically mounted and does not rotate, and hence there is very little friction between the pistons 18 and the wobble plate 28. The piston and cylinders are not subjected to excessive wear since the dynamic action of the elastic material lip on the piston tip tends to wipe off the solid contaminants which may otherwise adhere to the cylinder and piston walls.

In operation, rotation of the eccentrically positioned drive shaft assembly imparts a nutating motion to the nonrotating wobble plate 28. The pistons 18 are actuated on the discharge stroke by the wobble plate 28 and by the springs 26 on the suction stroke. Fuel enters the pump through the inlets 56 and 58 and flows through the internal channels to the inlet valves 68 which open automatically during the suction stroke and which close upon reversal of the piston motion, while the outlet valves 72 are automatically opened. Thus, on the discharge stroke fluid is discharged past the outlet valves 72 to the outlets 60 and 62.

The fluid exits through a port 74 but a small portion is diverted through a wash flow filter 78 and is pumped under higher than inlet pressure through the channel 52 and cross channels 54 in the shaft assembly 30. Thus, only filtered fluid is permitted to flow in the spaces between the various thrust and radial bearings supporting the shaft assembly 30 and the wobble plate 28.

It will be apparent to persons skilled in the art that the invention is subject to various modifications and adaptations. For example, it is within the scope of this invention to drive the pistons 18 with the wobble plate both on the discharge and suction strokes by interconnected opposed pistons.

What is claimed is:

1. In a wobble plate type pump, the combination comprising:

a cylindrical housing having a fluid inlet and a fluid outlet and containing a plurality of bores providing fluid passages and piston cylinders, the axes of said piston cylinders being parallel to the axis of said cylindrical housing, and pistons in said cylinders for pumping fluid from said inlet to said outlet;

an axial bore extending through said housing, said axial bore being positioned in unsymmetrical relationship with respect to the axis of said housing;

a rotatable drive shaft supported within said axial bore, said drive shaft including first and second opposed spaced bearing support surfaces having a perpendicular shaft extending therebetween, said surfaces being parallel to each other and at an angle of other than 90 degrees with respect to the axis of said shaft;

a wobble plate non-rotatably supported between said surfaces and surrounding said perpendicular shaft, said wobble plate having a surface at least on one side thereof in contact with said pistons for reciprocating substantially all of said pistons through a discharge cycle when nutated by rotation of said rotatable shaft whereby an unbalanced force is imposed on the Wobble plate;

a plurality of bearings for supporting said shaft within said housing and said wobble plate between said surfaces;

said bearings for said wobble plate being discs loosely supported solely by the wobble plate and each of the bearing support surfaces thereby insuring a relative rotational velocity intermediate both the bearing support surfaces and the wobble plate to increase their load carrying capacity;

and lubricating means for lubricating said plurality of bearings, said lubricating means preventing the flow of fluid from said inlet into contact with said bearrugs.

2. The invention as defined in claim 1 wherein said lubricating means comprises:

an axial fluid channel in said shaft and a plurality of cross channels extending from said axial channel to the space between said shaft and said bearings;

and a fluid connection between said outlet and said axial channel, said connection including a filter for said pumped fluid.

3. The invention as defined in claim 1 wherein said pistons are comprised of a reciprocating metallic shaft, and an elongated sleeve of elastic plastic material on said shaft, said sleeve providing a cylindrical surface over its entire length, said material providing a combination seal and Wear sleeve.

4. The invention as defined in claim 3 wherein said shaft is provided with an axial fluid channel and a plurality of cross channels extending from said axial channel to the space between said shaft and said bearings;

and a fluid connection between said outlet and said axial channel, said connection including a filter for said pumped fluid.

S. The invention as defined in claim 4 wherein the bearings for supporting said shaft within said housing are loosely fitted rotatable carbon graphite sleeves and loosely fitted rotatable-carbon graphite disks.

6. The invention as defined in claim 4 wherein said bearings for said wobble plate are carbon graphite disks.

References Cited UNITED STATES PATENTS 1,057,986 4/1913 Stevenson 103-162 1,184,406 5/1916 Bache 308-240 1,392,389 10/1921 Anderson 103-173 1,508,264 9/1924 Armentrout 92-182 1,776,786 9/1930 Eisenhauer 103-173 2,276,009 3/1942 Baldwin 92-182 2,500,719 3/1950 Ungar 103-126 3,117,419 1/1964 Brolund 103-173 3,272,079 9/ 1966 Bent 92-249 FOREIGN PATENTS 873,630 3/1953 Germany. 980,047 1/ 1965 Great Britain.

WILLIAM L. FREEH, Primary Examiner.

US. Cl. X.R. 308-240; 92-249 

